IPTG is a molecular biology reagent utilized in cloning experiments. This compound is used as a molecular mimic of allolactose, a lactose metabolite that triggers transcription of the lacoperon. Unlike allolactose, the IPTG sulfur (S) atom creates a chemical bond which is non-hydrolyzable by the cell, preventing the cell from "eating up" or degrading the inductant; therefore the IPTG concentration remains constant.

Isopropyl Î²-D-1-thiogalactopyranoside, abbreviated IPTG, is a molecular biology reagent. This compound is used as a molecular mimic of allolactose, a lactose metabolite that triggers transcription of the lac operon.